The present invention relates to a probe with electrodes for the capacitive measurement of liquid levels in a container.
Probes for level measurements according to prior art often rod-shaped and are arranged in the container so that a capacitor is formed between the probe and container wall. The capacitive value obtained is ideally a measure of the level in the container. In the case of such probes it is considered a drawback that a linear relationship between level and indication exists usually only the case of cylindrical geometry and that on account of the dependence of level measurement on the dielectric constant of the liquid. Because the level measurement is definite only in the case of a definite dielectric, errors may result during level measurement. Furthermore, the probe may not be arranged at arbitrarily great distances from the container wall, since for the purpose of exact level measurement the capacity variation along the length of the probe must be as great as possible. Furthermore, the desired linearity of level indication is obtained only when the probe is parallel with the container wall and existing built-in structures in the container.
A copending U.S. application by John B. Whitney, Ser. No. 481,127, filed June 20, 1974 issued as U.S. Pat. 3,935,740 on Feb. 3, 1976 for Liquid Level Probe describes a capacitor probe having a conductor strip running along the length of an enameled member. The measured quantity is the capacitance between the probe and the conductive tank in which it is mounted.
It is an object of the present invention to provide a probe having characteristics so that the capacitive level measurement may be carried out independently from the dielectric constant and conductivity of the liquid.